1. Field of the Invention
This invention relates to a method of manufacturing a thin film magnetic head having a first magnetic film constituting a bottom yoke, a second magnetic film constituting a top yoke, a thin film coil having the portion sandwiched between the first and the second magnetic films, a coil insulating film insulation-separating the thin film coil, a write gap film at least intervened between the pole portions of the first and the second m Oagnetic films opposing to a magnetic recording medium, and a substrate supporting the first and the second magnetic films, the thin film coil, the coil insulating film and a write gap film, particular a method of manufacturing a thin film coil head formed on a coil insulating film insulation-separating a thin film coil and having a precisely formed pole portion of a second magnetic film constituting a top yoke.
2. Related Art Statement
In a method of manufacturing a thin film magnetic head, normally, a second magnetic film constituting a top yoke is formed after a coil insulating film to support a first magnetic film (bottom yoke), a write gap film and a thin film coil are formed on a wafer. In forming the second magnetic film, a plated underfilm to form a second magnetic film is formed on the whole surface of the wafer including the coil insulating film by sputtering, for example. Next, a photoresist is applied on the surface of the plated underfilm, which is photolithography- processed to form a resist frame having an opening at the part for the second magnetic film to be formed. Subsequently, within the area surrounded by the resist frame, a second magnetic film is formed by a method such as an electroplating method. Although a plated film is film is deposited on the resist frame, it is removed.
One of the problems in the second magnetic film-forming process is that in the photolithography process to form a resist frame, a light for expose is reflected at the surface of the coil insulating film and the part of the photoresist except the area thereof to be defined by a photomask is exposed, resulting in the degradation of the pattern precision of the resist frame and thereby the degradation of the pattern precision of the second magnetic film.
The problem become conspicuous in the pole portion of the second magnetic film. The pole portion of the second magnetic film is opposed to the first magnetic film via the write gap film. The coil insulating film is positioned backward from the pole portion and rises up on the surface of the write gap film with inclined at a given angle. The starting point of the rising up is called as a "throat height=0 point", and the angle of the rising up is called as an "apex angle" which are important factor to determine the characteristics of the thin film magnetic head.
The second magnetic film is formed so as to constitute the pole portion parallel to the write gap film and the first magnetic film up to the throat height=0 point and be inclined at the apex angle toward the upper surface of the coil insulating film from the throat height=0 point.
Thus, in forming the resist frame for the second magnetic film, the photoresist part stuck on the inclined part at the apex angle toward the upper surface of the coil insulating film from the throat height=0 point must be exposed.
In this case, since the plated underfilm is stuck on the inclined part, the light for expose is reflected at the plated underfilm. The part of the reflected light is reflected toward the pole portion. Thus, the exposed pattern of the pole portion is different from the exposing pattern of the photomask, resulting in the pattern destruction of the resist frame corresponding to the pole portion.
The pattern destruction of the resist frame is a large obstacle for realizing a high recording density by narrowing a recording track width up to 1.0 .mu.m and below, for example.
Kokai publication No. 9-180127 discloses the technique that before applying a photoresist constituting a mask to form a magnetic film of a top yoke, an antireflection film is formed and on the antireflection film is applied a photoresist, which is exposed and developed, to form a resist frame as a mask for a second magnetic film. After forming the resist frame, the part of the antireflection film exposing to the bottom surface of the opening in the resist frame is removed by an ashing means, etc. and the second magnetic film is formed by plating, etc.
In the above conventional technique, the antireflection film exists in the whole bottom surface of the opening in the resist frame. The opening of the resist frame has a pole portion area corresponding to the pole portion of the top magnetic film and a yoke part area corresponding to a yoke part. Thus, the antireflection film has to be removed in both the pole portion area and the yoke part area.
However, the opening area in the pole portion area is remarkably different from that in the yoke part area. Moreover, for attaining a high density recording, the opening area of the pole portion area is inclined to be narrowed to a minute size of 1 .mu.m and below, for example. Thus, in removing the part of the antireflection film stuck on the inner pattern surrounded by the resist frame, the etching rate of the yoke part area is different from that of the pole portion area and it takes longer time in etching the pole portion area than in etching the yoke part area. As a result, during the removing the antireflection film in the pole portion area, the resist frame is remarkably etched, resulting in the broadening the width of the pole portion of the resist frame and the lowering the height of the resist frame. Such phenomena degrade the pattern precision of the second magnetic film and make difficult to form a magnetic film having a given thickness.